Section 5
SCSI Programming Guidelines
RC
-
READ
CONTINUOUS
(Byte
2,
Bit
4)
-
Se~
to one instructs the
ProD
rive
to
transfer
the requested length without adding delays which would increase data integrity, i.e., delays caused by
the
ProDrive', error recovery schemes. Thus, to maintain a continuous flow
of
data and avoid
delays, the
ProDrive will send data which may be erroneous; ignored errors will not create the
CHECK
CONOmON
status.
An
RC bit set to zero indicates that time-consuming operations for
error recovery are acceptable during data transfer. The default is zero.
TB
-
TRANSFER
BLOCK
(Byte
2,
Bit
5)
- Set
to
one,
if
DTE
bit
(bit 1
of
byte 2) is also
set to one, indicates that the failing block data (recovered
or
unrecoverable) will be transferred to the
initiator. A
TB
bit
of
zero, when
OTE
bit is set to one, indicates that the failing block will not be
transferred to the initiator.
If
DTE
is zero,
or
RC
is one, this
bit
is ignored.
On
unrecoverable errors,
TB
is checked regardless
of
the state
of
OTE. The default is zero.
ARRE
-
AUTOMATIC
READ
REALLOCATION
ENABLED
(Byte
2,
Bit
6)
-
Set
to
one
indicates that the ProDrive will enable automatic reallocation
of
bad blocks.
The
execution
of
the
automatic reallocation is similar
to
the function
of
the REASSIGN BLOCKS command,
but
is
initiated
by
the ProDriJle when a hard error is encountered, i.e., same non-zero
ECC
syndrome on
two
consecutive retries. (See Appendix A.)
An
ARRE
bit set to zero indicates that the ProDrive
will not perform automatic reallocation
of
bad blocks.
If
RC is one, this bit is ignored.
The
default
is
zero.
A
WRE
-
AUTOMATIC
WRITE
REALLOCATION
ENABLED
(Byte
2,
Bit
7)
-
Not,
supported by ProDrive. Must be set to zero by the initiator.
RETRY
COUNT
(Byte
2)
-
The
number
of
times the ProDrive will attempt to recover from
data
errors by rereading before applying correction.
The
default is 8.
CORRECTION
SPAN
(Byte
4)
- Specifies the size in bits
of
the largest read
data
error
on
which correction may
be
attempted.
It
can be set to values from 0-11; the default is 11.
NOTE: The Head Offset Count, Data Strobe Offset, and Recovery Time Limit (Bytes 5 - 7) are not
supported
by
ProDrive.
The
following table summarizes the valid modes
of
operation on the ProDrive.
SCSI
Programming
Guidelines
5-45
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